Feature: `docker kill --all` terminate all containers at once

Description

As a user when I'm building new projects I tend to spin up and kill a lot of containers for troubleshooting purposes.

Typically I do something like this alias dka='docker kill $(docker ps -q)', but I wonder why there isn't a flag for either docker stop or docker kill that does this.

If docker ps -q returns nothing, then naturally docker kill will display the help. Thus extra steps are needed in scripting to avoid this output.

Proposal

Could docker kill and/or docker stop have a -a/--all flag that terminates any available running containers? I imagine the -s flag could be used in combination like docker kill -a -s SIGQUIT

Another option would be docker killall which would allow for more in depth options like killall. This isn't necessary for my use case though.

If this is a valid feature, I'd like to give it a shot at implementing it 👍

Thank you

Start by locating the docker kill command entry point and its existing -s signal option, then compare the docker stop command. Clarify whether --all belongs on kill, stop, or both, and how it behaves when no running containers exist. Done means the chosen command supports the documented flag and its behavior is covered by the relevant CLI tests.